1. Field of the Invention
The present invention relates to a catalytic converter or reactor and a process for carrying out highly exothermic reactions.
2. Description of the Prior Art
Substantial difficulties are encountered in carrying out highly exothermic reactions where reactants and/or products are temperature sensitive. For example, the catalytic liquid phase reaction of propylene and hydrogen peroxide to produce propylene oxide is a highly exothermic reaction while hydrogen peroxide decomposition is quite temperature sensitive. Thus, removal of the exothermic heat of reaction without causing excess temperature rise presents a serious problem.
Conventional reactors for exothermic reactions are usually of two types:
(1) Quench type which consist of multiple fixed beds with cold feed quench injected in between beds
(2) Tubular type in which the catalyst is placed in the tubes of a vertical shell and tube heat exchanger
If the heat of reaction is high, the first type does not provide sufficient heat removal. This can be overcome by recycling cold reactor effluent but this results in the disadvantages associated with back-mixed reactors.
The tubular reactor cost becomes prohibitive when high heats of reaction have to be removed through heat exchanger surfaces operating with a low heat transfer coefficient. There is also a temperature gradient from the center of the tube which is often detrimental to a process which requires nearly isothermal conditions.
U.S. Pat. Nos. 2,271,646 and 2,322,366 provide catalytic converters for use in catalytic cracking and the like reactions wherein the converters are divided into a series of zones and the reaction mixture from one zone is removed and externally heated or cooled before being returned to the next reaction zone. Such converters are not suitable for the effective temperature and reagent concentration control of a highly exothermic system as is achieved in accordance with the present invention.